In the 19th to 20th centuries, many important steel structures were riveted, such as the Eiffel Tower, and the skeleton of automobiles. at the end of the 20th century, a large number of structures began to be welded, such as the skeleton of automobiles, but some structures that needed to be lightweight and had strength requirements, such as aircraft fuselages and steel bridges, used Machine Screw connections. What is the specific difference between riveted and screwed connections, and why are bridges screwed rather than welded?





The following are the characteristics of these three types of connections from different perspectives.
1. Load-bearing force. Riveted connections have a better shear capacity and a poorer tensile capacity. Dowel connections have good tensile and shear capacity. Welding is also tensile and shear can be, but afraid of tearing.

2. Removable. Dowel is a removable connection, while riveted and welded are not.

3. Quality assurance. Dowel > riveted > welded, welding is the least easy to carry out quality inspection, so civil aircraft with welding less.

4、 Change the material properties of the parts. Welding has the greatest impact, the residual stress deformation problem is more serious, for bridges and cars can still be tolerated, but the surface of the aircraft with high aerodynamic shape requirements is not ideal.

5、 Cost. Threaded connection is higher than riveted than welded.

6、 Adding excess weight. Threaded links are higher than riveted than welded.

7. Dissimilar material connection. For example, aluminum and titanium, composite and titanium, different series of aluminum alloy, welding is not very good, and it is common to connect different materials in aircraft, so it seriously affects the application scope of welding.

From the above comparison, you can know why cars and bridges are more often linked with welding and thread, and airliners are more often connected with riveting and thread.